The curable resin compositions heretofore used as sealants and adhesives for electrical/electronic components, for example, curable epoxy resin compositions, have yielded stiff, high-modulus cured products, resulting in a propensity for large stresses to be produced in the electrical/electronic component due to thermal expansion of the cured product; additional problems are warping of the electrical/electronic component or substrate, the appearance of cracks in the cured product itself, the generation of gaps between the electrical/electronic component and the cured product, and failure of the electrical/electronic component.
In order to reduce the stress associated with the cured product, a curable resin composition containing epoxy-functional silicone resin (refer to Japanese Laid-Open (Unexamined) Patent Application Number Hei 5-295084 (295,084/1993)), die-attach pastes comprising epoxy resin and the reaction product of cyanate resin with an epoxy-functional dimethylsiloxane compound (refer to Japanese Laid-Open (Unexamined) Patent Application Numbers Hei 10-147764 (147,764/1998) and Hei 10-163232 (163,232/1998)), and die-bonding materials comprising the reaction product of epoxy-functional silicone oil and a phenolic organic compound (refer to Japanese Laid Open (Unexamined) Patent Application Numbers Hei 7-22441 (22,441/1995), Hei 7-118365 (118,365/1995), and Hei 10-130465 (130,465/1998)) have been introduced. However, the cured products therefrom are still stiff and the stress-reducing effect is inadequate and there are limitations with regard to applications to electrical/electronic components.
In another vein, curable silicone compositions provide cured products that have excellent electrical characteristics, e.g., dielectric characteristics, volumetric resistivity, and dielectric breakdown strength, and for this reason are used as sealants and adhesives for electrical/electronic components. However, they yield cured products that are, conversely, soft and that have a low strength and a low modulus, and this has resulted in a poor capacity to protect electrical/electronic components, that is, a poor performance with regard to protecting electrical/electronic components from external impact or shock. In addition, these cured products, because they exhibit low adhesiveness for electrical/electronic components, have been associated with the facile generation of gaps between the cured product and these components. While there have been attempts at lowering the thermal expansion coefficient of the soft cured product by incorporating filler, this results in a loss of the softness and flexibility.
Japanese Laid Open (Unexamined) Patent Application Number Hei 6-306084 (306,084/1994) discloses a curable silicone composition that has a short gelation time; this curable silicone composition comprises epoxy-modified silicone oil and phenol-modified silicone oil. This curable silicone composition, however, exhibits a poor curability and requires a lengthy period of heating for cure. In addition, it generates a very brittle cured material.
It is an object of the present invention to provide a curable silicone composition that exhibits excellent handling and curing characteristics and that cures to give a cured product that is very flexible and highly adhesive. It is a further object of the present invention to provide highly reliable electronic components.